func distMoney(money int, children int) int {
	if money < children {
		return -1
	}
	if money > 8*children {
		return children - 1
	}
	if money == 8*children-4 {
		return children - 2
	}
	// money-8x >= children-x, x <= (money-children)/7
	return (money - children) / 7
}